More than a year has passed since welterweight contender Robert Guerrero's last fight, and that outing was not a memorable one for him.

After more than a year of calling out pound-for-pound king Floyd Mayweather Jr., Guerrero finally got his chance to challenge the welterweight champion in May 2013. But instead of the glorious victory Guerrero had predicted, "The Ghost" was outclassed as Mayweather dominated the fight, as usual, en route to a lopsided unanimous decision by identical scores of 117-111.

The loss sent Guerrero into a 13-month layoff, one that will end when he faces Yoshihiro Kamegai of Japan on Saturday (Showtime, 10 p.m. ET, with preliminary bouts on Showtime Extreme beginning at 8 p.m. ET/PT) in the scheduled 12-round main event of a tripleheader at the StubHub Center in Carson, California.

"I'm back, and I can't wait. It has been a year already, so it's way overdue," Guerrero said. "I had a good rest, and through that downtime, while I was resting, I was keeping in shape. I'm feeling great."

Also on the card, decorated amateurs and former ESPN.com prospects of the year Gary Russell Jr. (24-0, 14 KOs), a 26-year-old 2008 U.S. Olympian from Capitol Heights, Maryland, and Vasyl Lomachenko (1-1, 1 KO), 26, a two-time Olympic gold medalist for Ukraine, will meet for a vacant featherweight world title in the co-feature.

In the scheduled 10-round opening bout, former two-division titleholder Devon Alexander (25-2, 14 KOs), 27, of St. Louis, will look to bounce back from losing his welterweight belt to Shawn Porter in December when he takes on Jesus Soto Karass (28-9-3, 18 KOs), 31, of Mexico.

Guerrero, who has won world titles at featherweight and junior lightweight as well as interim belts at lightweight and welterweight, said part of the reason for the extended layoff was because he had three tough fights -- decision wins against Selcuk Aydin and former welterweight titleholder Andre Berto and the loss to Mayweather -- in a 10-month span.

Robert Guerrero attributes his 13-month layoff in part to recovery time needed after three tough fights in a short span. Gene Blevins/Hoganphotos/Golden Boy

"The Aydin fight was a tough, 12-round fight with him, a hard puncher. Then I had the tough fight with Berto too. We went at it for 12 rounds and then also the Mayweather fight," Guerrero said. "Those training camps are brutal, and they were real close together. So I took a little bit of time to recover and recoup and I'm back. Jan. 1, I was back in the gym training."

But it wasn't only tough fights that kept Guerrero, 31, of Gilroy, California, on the sideline. It was problems with his promoter, Golden Boy. Guerrero (31-2-1, 18 KOs), for reasons never fully articulated, attempted to break his promotional contract earlier this year through arbitration with the California State Athletic Commission. The commission denied Guerrero's request for a hearing because his promotional agreement is governed by New York law. Guerrero's attorney threatened to sue Golden Boy but never did. In March, Guerrero signed with powerful adviser Al Haymon and, voila, the issues with Golden Boy suddenly went away, at least enough for Saturday's fight to be arranged.

Asked if things had been worked out between him and the company, Guerrero declined to get into it.

"When you have the legal actions, you want to take care of that, and my management took care of a lot of stuff," he said. "I leave that stuff to my management. They took care of all that. I'm back in the ring on Saturday, and I'm ready to fight. That's where my focus is."

Golden Boy president Oscar De La Hoya was not the one who dealt with Guerrero's promotional issues. That fell to Richard Schaefer, but he resigned as CEO earlier this month. When pressed about Guerrero's promotional situation, De La Hoya offered only, "We're extremely happy to be promoting this fight on Saturday, and we're looking forward to promoting many, many more fights in the future."

But does Guerrero remain under contract?

"That's something we'll discuss in the future, so I have no comment," De La Hoya said.

Whatever his contract status, Guerrero has what could be a tough fight in front of him against a determined boxer in the 31-year-old Kamegai, a powerful puncher who will be fighting in the United States for the fourth time.

How fresh will Guerrero be after such a lengthy layoff?

"Having a little bit of time off helps your body recuperate, your joints and everything," Guerrero said. "But don't get it wrong. There's always ring rust. Everybody always says they feel great, they feel the best, but everybody has a little ring rust."

Kamegai (24-1-1, 21 KOs) has been much more active, fighting three times since Guerrero's last bout. In his most notable bout, which took place at the StubHub Center last June, Kamegai dropped a unanimous 10-round decision to Johan Perez, who later dropped down in weight and won an interim junior welterweight belt.

"I'm from Japan, and we respect everybody outside the ring," Kamegai said through a translator. "There is no trash talk. In Japan, we think of Robert Guerrero as a multidivision world champion who fought Floyd Mayweather. That said, I didn't fly all the way across the ocean to lose. I came here to not just win the fight but to have a decisive victory.

"I'm very confident, and I feel I'm acclimated. What I've worked on most since arriving is a way to avoid all his holding tactics and a way to keep him from being able to fight from long range. This is a very important fight and a tremendous opportunity for me. Not a lot of people know me now, but they will after the fight."

Japan's Yoshihiro Kamegai hopes to make a name for himself in the United States with a victory on Saturday against Robert Guerrero. Gene Blevins/Hoganphotos/Golden Boy

While Kamegai is hoping to make a name for himself, Guerrero is hoping to get back on the winning track. He said he learned from the loss to Mayweather.

"You've got to learn from experiences like that," he said. "I lost to the best fighter in the world. You want to get better, you want to get stronger, you want to get faster. Seeing the type of foot speed he had and hand speed in front of me, it makes you want to step your game up more. So it really lit a fire under me to become a better fighter, to start using every tool that I have and not just get put into one dimension where I started walking guys down, like I did with Berto, and trying to be that big man and trying to have muscles."

Guerrero said he hopes that a win against Kamegai will move him toward a rematch with Mayweather, as unlikely as a second fight probably is.

"There's a long road, and I know Mayweather has three more fights lined up for him [under his Showtime/CBS contract], and I'll try to get back into that position and give it another shot," Guerrero said. "I felt it wasn't the best of me in there, and you tend to follow to certain styles, trying to be the guy just walking guys down where you've got a lot more God-given abilities that you've got to put to use.

"So there's a lot more that I can bring to the table when I fight. I wasn't really satisfied with my performance then, and I want to get back up and make it happen."